Mechanisms of inflammasome activation and pyroptosis induction by HIV

在未经治疗的患者中，HIV进展期间CD 4 T细胞的进行性丧失导致临床综合征AIDS。在HIV感染过程中，活化的CD 4 T细胞通过caspase-3介导的凋亡而死亡。然而，在HIV感染期间死亡的绝大多数CD 4 T细胞（超过95%）是静止的淋巴CD 4 T细胞。最近，已经发现这些静止的淋巴CD 4 T细胞在HIV感染后经历半胱天冬酶-1介导的细胞死亡而不是凋亡。据认为，异常核酸是在所谓的流产感染过程中产生的，其被核核酸传感器IFI 16直接识别。IFI 16又与衔接蛋白ASC一起在核旁区域形成活性炎性体，导致半胱天冬酶-1的自动蛋白水解激活。活性半胱天冬酶-1通过蛋白水解激活IL-1b细胞因子家族成员并介导细胞凋亡。值得注意的是，外周静止CD 4 T细胞不会在HIV感染时死于IFI 16介导的焦亡，除非它们接收到来自淋巴静止CD 4 T细胞的信号。IFI 16炎性小体的细胞类型和活化依赖性诱导以及随后的焦萎细胞死亡的潜在机制仍然不清楚。我们已经在巨噬细胞中进行了广泛的化学生物学筛选，以更好地了解其他触发因素激活炎性小体的机制。我们的初步数据表明，许多特定的信号通路的作用，以控制炎性小体激活和影响的炎症反应的各种触发器的阈值。在本提案中，我们的目标是扩展这些研究，并在感染HIV的人淋巴聚集体培养物（HLAC）中进行化学生物学筛选，以更好地了解驱动IFI 16炎性小体形成和细胞凋亡诱导的机制。通过一个综合的合作研究计划，我们的目标是确定和验证新的因素在HIV限制静止的CD 4淋巴CD 4 T细胞。我们还旨在验证这些新发现的途径是否更普遍地调节其他细胞类型中其他炎性小体和细胞凋亡的形成。

The progressive loss of CD4 T cells during HIV progression in non-treated patients leads to the clinical syndrome AIDS. Activated CD4 T cells die through caspase-3 mediated apoptosis during HIV infection. However, the large majority of CD4 T cells (more than 95%) that die during HIV infection are quiescent lymphoid CD4 T cells. Recently, it has been discovered that these quiescent lymphoid CD4 T cells undergo caspase-1 mediated pyroptotic cell death rather than apoptosis after HIV infection. It is thought that aberrant nucleic acids are produced during the process of so-called abortive infection which are directly recognized by the nuclear nucleic acid sensor IFI16. IFI16, in turn, forms an active inflammasome together with the adapter protein ASC in a paranuclear area leading to auto-proteolytic activation of caspase-1. Active caspase-1 proteolytically activates members of the IL-1b cytokine family and mediates pyroptosis. Of note, peripheral quiescent CD4 T cells do not die from IFI16-mediated pyroptosis upon HIV infection, unless they receive signals from lymphoid quiescent CD4 T cells. The mechanisms underlying the cell type and activation dependent induction of the IFI16 inflammasome and subsequent pyroptotic cell death remain ill defined. We have performed extensive chemical biology screens in macrophages to better understand the mechanisms of inflammasome activation by other triggers. Our preliminary data show that many specific signaling pathways act to control inflammasome activation and influence the threshold of inflammasome responses to various triggers. In this proposal we aim to extend these studies and perform chemical biology screens in human lymphoid aggregate cultures (HLAC) infected with HIV to gain a better understanding of the mechanisms driving IFI16 inflammasome formation and pyroptosis induction. Through an integrated collaborative research plan we aim to identify and verify novel factors acting in HIV restriction in quiescent CD4 lymphoid CD4 T cells. We also aim to verify whether these newly uncovered pathways more generally regulate the formation of other inflammasomes and pyroptosis in other cell types.